Why Does Blender Distort UV Maps By Default?
It depends on the model you have as well as the UV deployment method you have chosen, and where you have marked your seams.

The following is documentation on the general workflow of UV unwrap and its use in industry https://conceptartempire.com/uv-mapping-unwrapping/

Here is a blender tutorial on how UV works https://www.youtube.com/watch?v=Y7M-B6xnaEM

In this other tutorial you will see more advance UV workflow of blender https://www.youtube.com/watch?v=L3654VGZObg&amp;feature=emb_title

Notably through the use of add-ons simplifying life by integrating tools to optimize the UV space(Tex tools, UV Packmaster...).